1. Field of the Invention
The present invention relates to a method and related apparatus for obtaining images for use in displaying a three-dimensional illusion of a subject volume having foreground and background portions as viewed by an observer having binocular vision. The related apparatus comprises a support apparatus for one or more imaging devices used to obtain images for displaying a three-dimensional illusion in accordance with the method of the present invention.
II. Background Information
Production of two-dimensional images which may be used to provide a three-dimensional illusion is a long outstanding goal in the visual arts field. The development of methods and related devices for producing such three-dimensional illusions has to some extent paralleled development in the field of physiology of depth perception. When viewing a scene naturally having depth, the human brain is believed to perceive depth for objects in the scene from a number of sources, called depth cues. Lighting effects, such as shading and color tones, can provide important depth information. In addition, perspective, overlapping and the relative size, texture, and angle or gradient of objects in the scene may provide depth information. The relative motion of the objects may also allow the brain to perceive depth.
Another important depth cue is parallax, i.e., depth information provided by comparing the images of the same scene from each eye. The distance between the center points or irises of the eyes for an average human being, generally referred to as the interocular distance, is approximately 65 millimeters. Behind the iris of each eye is a planar retina. The retina receives light from the subject volume and forms a two-dimensional image of the subject volume. The two-dimensional image at each retina is transferred to the brain by electrical impulses. The brain is then believed to iteratively compare the two-dimensional images to obtain a single image of the subject in which the various objects in the subject appear to have depth. The rate of comparison in the brain of the two-dimensional images formed at the retina, generally referred to as the visio-psychological suppression or memory rate, appears to be approximately eight to ten times per second.
This process of obtaining a three-dimensional illusion of a subject volume is referred to as the process of binocular vision originating at left and right points of origin, namely the left and right eyes of a human observer.
Various approaches have been used in the past to obtain images having the appearance of depth. One commonly used approach is to obtain images from a scene from two horizontally displaced viewing points or points of origin. The horizontal displacement of the points of origin is generally equal to or less than the interocular distance. Images obtained from these two points of origin are simultaneously superposed on a projection screen, but the light forming these images is polarized differently for the images from the left point of origin than for images from the right point of origin. Accordingly, it is necessary for the observer to wear glasses having approximately polarized lenses. While this method produces images perceived by the viewer as having depth, the extent of the field, referred to herein as depth quality, tends to be overly exaggerated and often results in discomfort to the viewer. The necessity of wearing glasses having polarized lenses is inconvenient. In addition, the necessity of projecting multiple images having differing polarization makes it difficult or impossible to use conventional electronic or mechanical projection equipment.
A similar approach used in the past involved obtaining images from horizontally displaced left and right points of origin, as described above, and projecting those images alternately rather than simultaneously. An example of such a system is disclosed in U.S. Pat. No. 4,303,316 issued to McElveen. U.S. Pat. No. 4,006,291, issued to Imsand, adopts a form of this approach in which images from one point of origin are primarily used while images from another point of origin are periodically inserted.
More recently, approaches using vertical alignment of the viewing points, generally referred to as vertical parallax, have been proposed. An example of a vertical parallax system is disclosed in U.S. Pat. No. 4,429,328, issued to Jones, Jr., et al. Empirical evidence shows that the vertical parallax approach produces the appearance of depth while being more amenable or comfortable to the viewer.
A principle drawback of the use of alternating images from two viewing points, whether using the horizontal or vertical displacement approaches, is that slowly moving or stationary objects in the scene being viewed tend to move or rock as the point of origin alternates. This rocking phenomenon is attributable to the different viewing angles corresponding to the respective points of origin.
Accordingly, it is an object of the present invention to provide a method for obtaining images for use in displaying a three-dimensional illusion of a subject volume and related apparatus for producing enhanced depth images, having reduced motion (rocking) effects.
Additional objects and advantages of the invention will be set forth in the description which follows and in part will be obvious from the description or may be learned by practice of the invention.